Sand control system and method for controlling sand production

ABSTRACT

A method for controlling sand production in a well drilled in a subterranean formation comprising installing an expandable sand screen assembly in the well. The expandable sand screen assembly comprises an expandable sand screen in an unexpanded configuration. A slurry is pumped down the well and circulated through the annular space defined by the expandable sand screen and the formation. The expandable sand screen is expanded thereby dehydrating the slurry in the annular space.

REFERENCE TO PRIOR APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/972,013, filed Sep. 13, 2007, which is incorporated herein byreference.

FIELD OF INVENTION

The present invention relates to a sand control system and a method forcontrolling sand production in a long horizontal or deviated well.

BACKGROUND

The art of completing wells to exclude solids particles produced by wellfluids is commonly known in the literature as gravel packing. In manywell completions, unwanted formation solids (e.g. sands, fine materials,and other debris) are produced into the well along with the productionfluids. These solids are often undesirable and many methods of stoppingthese solids from flowing into the well whilst producing the fluids arewell defined.

A common technique for controlling the production of particulates from awell is known as “gravel packing.” In a typical gravel pack completion,a well screen is lowered into the wellbore and positioned across theinterval of the well that is to be completed. Particulate material,collectively referred to as gravel, is then pumped as a slurry down thetubing on which the screen is suspended. The slurry exits the tubingabove the screen through a “crossover” tool or the like and flowsdownward in the annulus formed between the screen and the well casing oropen hole, as the case may be.

The liquid in the slurry flows into the formation and/or the openings inthe screen that are sized to prevent the gravel from flowing throughthem. As the fluid is drawn out of the slurry it dehydrates. Thisresults in the gravel being “screened out” on the screen and in theannulus around the screen where it collects to form the gravel pack. Thegravel is sized so that it forms a permeable mass which blocks the flowof any particulates produced with the formation fluids.

Gravel packing fills the annular space between the formation and ascreen with a clean well-sorted sand or gravel. The gravel pack forms avolumetric filter that prevents fines from plugging the screen and sandfrom entering the well. It structurally supports the formation, and itprevents flow in the annulus between screen and the open hole. All ofthese features increase the completion's durability in weak andheterogeneous formations; however, conventional methods for gravelpacking vertical wells are not suited for long horizontal wells.

One of the main problems with gravel packing, especially when longhorizontal or inclined intervals are completed, is obtaining uniformdistribution of the gravel along the entire completion interval andcompletely packing the annulus between the screen and the casing (incased hole completions) or between the screen and the wellbore (in openhole completions). Incomplete packing of the interval resulting invoids/unpacked areas in the gravel pack is often caused by the improperdehydration of the gravel slurry into portions of the formationinterval. This can occur because the pressure required to pump the fluidslurry into the production interval may exceed the fracture pressure ofthe formation, which results in the liquid carrier of the fluid slurryleaking off into the formation. Improper dehydration causes theformation of gravel “bridges” in the annulus before all of the gravelhas been placed. These bridges block the transport of slurry past thebridge. This results in the insufficient placement of the gravel becausegravel fails to fill the annulus downstream of the bridge. Subsequently,the portion of the screen that is not covered or packed with gravel isthereby left exposed to erosion by the solids in the produced fluids orgas and/or that portion of the screen is then easily blocked or“plugged” by formation particulates, that would have been filtered outof the inflow by a properly placed gravel pack.

Consequently, a number of methods for installing sand control in longhorizontal (greater than 200 m) or deviated wells (greater than 80° fromvertical) have been developed. One technique used to reduce the requiredpressure for gravel packing a long production interval that is inclined,deviated or horizontal is the alpha-beta gravel packing method describedin U.S. Pat. No. 6,311,772 which is hereby incorporated by reference. Inthis method, the gravel packing operation starts with the alpha wavedepositing a bed of gravel on the low side of the wellbore progressingfrom the near end (heel) to the far end (toe) of the productioninterval. Once the alpha wave has reached the far end (toe), the betawave phase begins wherein gravel fills the high side of the wellbore, ontop of the alpha wave deposition, progressing from the far end (toe) tothe near end (heel) of the production interval. Shunt tubes mayoptionally be installed to allow an alpha wave to by-pass a bridge orobstruction so that it can continue past the blockage and propagate downthe open hole to the toe.

A drawback of the alpha-beta method is that it is sometimes madeimpractical by logistical considerations including the uniformity of thecompletion zone, the availability of fluid storage, and the type ofcarrier fluid used. Gravel packs are more tolerant to non-uniform andheterogeneous completion zones but have installation risks that makethem unsuitable for some long horizontal wells in low strength,unconsolidated formations. Additionally, fluid storage and handlingvolumes are limited for some rigs especially in remote locations.Conventional horizontal alpha-beta methods use low sand concentrationsand require large volumes of clean fluid to deploy. The required volumesfor alpha-beta packs increase in low fracture gradient environments,where low sand concentrations must be used. Conventional alpha-betapacking uses water-based carrier fluids. In cases where the reservoirsection must be drilled with oil-based or synthetic-based drillingfluid, usually the open hole must be displaced to a water based fluidprior installing the screens and gravel pack. This increases theprobability of a hole collapse or other hole problems that could resultin an incomplete or failed gravel pack job.

Expandable sand screens (ESS) were developed for use in long horizontalwells as an alternative to gravel packs in combination with conventionalscreens. An example of a method utilizing ESS technology is in U.S. Pat.No. 5,901,789, which is hereby incorporated by reference. When expansionis large enough to eliminate most or all of the annular space betweenthe formation and the expanded screen, annular flow can be limited orprevented. When the expandable screen is in continuous contact with theformation (referred to by those skilled in the art as “full compliantexpansion”), it supports the formation and prevents disaggregation ofthe rock that could release fines and sand particles that might erode orplug the screen.

Because the amount of expansion that is possible with ESS systems,expandable sand screens do not always achieve full compliant expansionleaving an annular space between the screen and the formation. Anysignificant gap between the screen and open hole defeats some of theperceived benefits of ESS. Additionally, expandable sand screens havefeatures that limit their application to formations with uniform grainsizes where they are most likely to be successful. Other ESS designparameters such as screen aperture sizes, mesh type, unexpanded screendiameters, and expansion ratios are also not robust to uncertainties inrock quality encountered while drilling long lateral sections.

Thus there is a need for a reliable method of installing sand control inlong horizontal or deviated wells.

SUMMARY OF THE INVENTION

The invention includes a method for controlling sand production in awell drilled in a subterranean formation comprising installing anexpandable sand screen assembly in the well. The expandable sand screenassembly comprises an expandable sand screen in an unexpandedconfiguration. A slurry of gravel and carrier fluid is circulated intothe annular space between the unexpanded expandable sand screen and theformation or between the unexpanded expandable sand screen and thecasing. In one embodiment, a slurry of gravel and carrier fluid ispumped down a tubular inside the expandable sand screen assembly andcirculated up through the annular space between the expandable sandscreen and the formation. Alternatively, a slurry is pumped through acrossover tool above the sand screen into the annulus between theformation and the unexpanded expandable sand screen, where fluiddisplaced by the slurry is circulated up a tubular inside the expandablesand screen assembly. The expandable sand screen is expanded, therebydehydrating the slurry in the annular space. The method furthercomprises forming a gravel pack behind the expandable sand screen.

The inventions also include a sand control system comprising a welldrilled in a formation, an expandable sand screen installed in anexpanded configuration, an annular space located between the outersurface of the expandable sand screen and the formation, and a gravelpack located in the annular space. According to one embodiment of theinvention, the gravel pack was dehydrated by expanding the expandablesand screen.

The inventions also include a method for producing oil or gas comprisingdrilling a well in a subterranean formation comprising, installing anexpandable sand screen assembly comprising an expandable sand screen inan unexpanded configuration into the well, pumping a slurry down thewell, circulating the slurry through an annular space defined by theexpandable sand screen and the formation, expanding the expandable sandscreen thereby dehydrating the slurry in the annular space and producingoil or gas from the well.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is better understood by reading the followingdescription of non-limitative embodiments with reference to the attacheddrawings, wherein like parts of each of the figures are identified bythe same reference characters, and which are briefly described asfollows:

FIG. 1 illustrates a well with an expandable sand screen in anunexpanded configuration during circulation of a slurry.

FIG. 2 illustrates the expandable sand screen as it is expanded andbeing used to dehydrate the slurry.

DETAILED DESCRIPTION

Referring to FIG. 1, a wellbore 101 is shown drilled in a subterraneanformation 102. In the embodiment shown, wellbore 101 is an open holewellbore; however the invention could theoretically be practiced in acased wellbore environment.

An expandable sand screen (ESS) assembly 103 is run in an unexpandedconfiguration into wellbore 101 using a workstring (not shown). The ESSassembly may include any combination of expandable sand screens 104,blank sections of pipe, collapsible centralizers or external packers(not shown). Prior to installing ESS assembly 103, additional tools mayhave been installed in the well including landing tools (not shown) fora wash pipe 105 and an expansion tool (not shown in this Figure). Washpipe 105 could alternatively be run simultaneously as part of the ESSassembly 103.

If not already deployed as part of the ESS assembly, wash pipe 105 isrun inside expandable sand screen 104. A slurry consisting of gravelpack sand or ceramic proppant suspended in a carrier fluid is pumpeddown wash pipe 104 and circulated into the annular space 107 betweenexpandable sand screen 104 and the wall of formation 102. The directionof circulation of the slurry is shown by arrows 106. Optionally leadingspacers or chemical treatments may be pumped ahead of the slurry toimprove open hole displacement and wellbore clean up. The slurry mayinclude internal breakers or other chemicals needed to facilitate theclean up the gravel pack once deployed for oil, synthetic, or waterbased fluid systems.

After the slurry is circulated, wash pipe 105 is pulled out of thewellbore and may be used to pick up the parts of ESS assembly 103 whichare no longer needed. Alternatively, these parts of the ESS assembly maybe retrieved on a subsequent trip into the well. In another embodiment,the expansion tool assembly could be parked in an expansiontool-launching sub at the top of the ESS assembly, so that when thelower end of the wash pipe engages the expansion tool. Once engaged, thecombined assembly is ready to expand the screen. The gravel pack sand orproppant remains disposed between expandable sand screen 104 and theborehole, forming a gravel pack, albeit one in which significant liquidmay be present.

As shown in FIG. 2, expandable sand screen 104 is then expanded usingexpansion tool 201. Expansion tool 201 may be any conventional expansiontool known in the art known including but not limited to expansion pigs,cones, and mandrels. Expansion of expandable sand screen 104 may beaccomplished using a top down or bottom up expansion method. In oneembodiment, expandable sand screen 104 is expanded against or intoformation 102; however, expandable sand screen 104 may also be partiallyexpanded or expanded to a threshold just before being expanded into oragainst the formation.

FIG. 2 shows expandable sand screen 104 in an expanded configuration.Expansion of expandable sand screen 104 pushes the outside of the screentoward the wall of the formation. A force is applied in the direction ofarrows 210 thereby compressing annular space 107. This properly anduniformly dehydrates the slurry 202 in annular space 107 betweenexpandable sand screen 104 and the wall of formation 102. The expansionforce prevents the formation of voids in the gravel pack during thedehydration process. As the slurry is dehydrated, gravel pack 203 iscompressed behind expandable sand screen 104, filling voids due to holeirregularities or wash outs.

When the expansion is complete, the work string used to deploy theexpansion tool is pulled out of the hole. If needed, the work string maybe used to place breakers or other chemicals along the completion as itis pulled back inside the newly expanded screen.

Installation of a gravel pack according to this method limits thenecessary fluid volumes needed to deploy the completion. Consequently,this method can be deployed in regions where logistics and fluid storagemakes alpha-beta packing impossible or impractical.

This method of installation may also increase the probability of successof an open hole completion in sections that are drilled withnon-water-based (non-aqueous) drilling fluids. Unlike gravel packing viathe alpha-beta method, this method is compatible with a wellbore inwhich oil-based or synthetic drilling fluid was used.

Installation of a gravel pack in this method may provide backupinsurance of gravel covering screen if the expansion is not sufficientto protect against fines liberation on hole collapse and fines pluggingthe entire screen. The slurry volume and concentration may be varied tomake up for an out of gauge hole if drilling conditions become unstableor difficult.

One of the advantages cited for expandable sand screens that areexpanded against the formation is that fines in the unconsolidatedformation are “locked” in place because deforming and disaggregating ofsand is limited as the well is drawn down. Because open holes are rarelyexactly in gauge or circular, the fluid sand slurry can move to fill thespace and provide full contact between the expanding screen andformation. Expansion according to this method increases the probabilitythat this “fines locking” stress is applied uniformly along the openhole.

Those of skill in the art will appreciate that many modifications andvariations are possible in terms of the disclosed embodiments,configurations, materials, and methods without departing from theirspirit and scope. Accordingly, the scope of the claims appendedhereafter and their functional equivalents should not be limited byparticular embodiments described and illustrated herein, as these aremerely exemplary in nature and elements described separately may beoptionally combined.

1. A method for controlling sand production in a well drilled in asubterranean formation comprising: a) installing an expandable sandscreen assembly comprising an expandable sand screen in an unexpandedconfiguration into the well; b) pumping a slurry down the well; c)circulating the slurry through an annular space defined by theexpandable sand screen and the formation; and d) expanding theexpandable sand screen and thereby dehydrating the slurry in the annularspace.
 2. The method of claim 1, further comprising forming a gravelpack behind the expandable sand screen.
 3. The method of claim 2 whereinthe expandable sand screen is expanded so that the gravel pack iscompressed in step d).
 4. The method of claim 3 wherein step d) isperformed by displacing an expansion device through the expandable sandscreen wherein the expansion device is selected from the groupconsisting of expansion pigs, mandrels, and cones.
 5. The method ofclaim 4 wherein the expandable sand screen assembly further comprisesblank sections of pipe, additional sections of expandable sand screens,collapsible centralizers, expansion tools, or external packers.
 6. Themethod of claim 5 wherein the well is a long horizontal or deviatedwell.
 7. The method of claim 6 wherein step b) comprises: pumping theslurry through a tubular inside the expandable sand screen assembly. 8.The method of claim 6 wherein step b) comprises: pumping the slurrythrough a crossover tool into the annular space.
 9. A sand controlsystem comprising: a well drilled in a formation; an expandable sandscreen installed in the well in an expanded configuration; an annularspace located between the outer surface of the expandable sand screenand the formation; and a gravel pack located in the annular space;wherein the gravel pack was dehydrated by expanding the expandable sandscreen.
 10. The sand control system of claim 8 wherein the well is ahorizontal or deviated well.
 11. A method for producing oil or gascomprising: a) drilling a well in a subterranean formation comprising:b) installing an expandable sand screen assembly comprising anexpandable sand screen in an unexpanded configuration into the well; c)pumping a slurry down the well; d) circulating the slurry through anannular space defined by the expandable sand screen and the formation;e) expanding the expandable sand screen thereby dehydrating the slurryin the annular space; and f) producing oil or gas from the well.
 12. Themethod of claim 11 wherein step c) comprises: pumping the slurry througha tubular inside the expandable sand screen assembly.
 13. The method ofclaim 11 wherein step c) comprises: pumping the slurry through acrossover tool into the annular space.